Bloodletting

In not-so-ancient times, many people relied on bloodletting as a way to treat and cure a wide variety of ailments ranging from sore throats to acne. Fortunately, the procedure's popularity died once more modern and fine-tuned treatments became available.

Tapeworms

At one point in history, tapeworms were marketed toward hopeful dieters looking for an easy way to shed a few extra pounds. Many would hope by playing host to these hungry parasites, they would considerably cut down their caloric intake. Unfortunately being infected with tapeworms carries many side effects, including abdominal pain, fatigue, nausea, bloating, and diarrhea just to name a few. Ingesting tapeworms for weight loss has since been banned in America.

Lobotomies

The lobotomy is an intensely invasive surgery involving severing nerve pathways in the brain, which was developed to treat severe mental illness in the 1930s. Although the procedure earned its creator a Nobel Prize, many quickly realized the lobotomy often came with its fair share of extreme side effects. Lobotomies were a common practice for two decades until advances in antipsychotic medication began to surface in the 1950s

Radium

Although radium is still currently used in medicine, its original uses were found to have negative side effects on humans. While radium was (and is) primarily used to treat cancer, it was often considered to be a cure-all, namely applied to ailments like impotence. Old-school radium treatments often lead to other medical complications, such as loss of limbs or even lives. Thankfully, radium use has become safer over the years, as doctors continue efforts to learn more about the drug.

Mercury

Mercury aka "quicksilver" has been used to treat many ailments, namely syphilis (following a massive epidemic in the 1490s), skin conditions, and cavities. Despite its benefits, mercury use has been highly controversial due to its extreme toxicity. Prolonged exposure has been known to cause neurological damage, infertility, and complications with bone marrow.

Tobacco

For many centuries, tobacco was thought of as the solution for many different medical troubles. Headaches, colds, fatigue — you name it. It wasn't until the mid 20th century that tobacco use was found to be extremely detrimental to human health.